The XMOS XCore chip in the X1000 is not "software re-writable". It's just a CPU, not an FPGA. Big difference.
I know it's not an FPGA. As for software re-writable, well it is programmable. The question of exactly how this will be implemented in the X1000 is still unclear as far as I am aware.
According to some it's great, according to others it's a waste of silicon. TBH I'll wait and see what comes of it and I'll wait and see what comes of Intels FPGA offering too.
It may be worthwhile as a UAE + chipset in FPGA offering but the way minimig is steaming along it'll have some catching up to do, I don't see the point for Amigans to get exited yet.
Edit:
Then again, it could be interesting to see what the AROS fans have to say about it. mmm...